Thursday, December 13, 2012

Is Running Bad For Your Heart?

Now here’s a funny thing: I was about to write a few linked posts about the importance of exercise for health and the difficulties of changing habits and persuading  adults to make even a minimal effort, when I came across an article warning that exercise might have dangers. (Not that there's anything in it to change my plans as only good things can happen if someone moves from inert to 150 minutes a week). No the dangers are for those who are are worried about their health but for those who become intoxicated by the challenges, the idea of pushing back physical limits, and addicted to the feeling of being both physically empty and extremely satisfied.  Doing too much, or more specifically taking part in endurance events like marathons, triathlons, or ultramarathons might not actually be too healthy. There may be some unwanted adaptations to the heart and it is possible there is a dose effect so that just as too little exercise is bad for a body running too much might not be so good!

The origin of the concern was a paper has been published in Mayo Clinic Proceedings entitled ‘Potential adverse cardiovascular effects from excessive endurance exercise’ and many of you might not want to read any further than the title. Feel free to close your eyes, put your fingers in your ears, say “I am not listening!’ or ‘this cannot possibly be right because I don’t want to believe it’. If you write for a newspaper you can do this at slightly greater length. That’s OK as long as you are clear in your mind why you run and know that if you run for more than about 30 minutes a day you do so for reasons other than health.  However although we might want to continue doing what we do we should not treat unwelcome sounding research like and leave it unopened like an unwanted bank statement. We must face it dispassionately to see what the researchers actually say and be prepared to put aside our preconceptions. Before doing so though we can be strengthened by the thought that what is actually proved in any scientific papers is usually very specific within precisely defined limits which often do not bear the weight of the more generalised (and lurid) headlines.

So what to make of the Mayo paper?  Well from my lofty position of a non-expert it looks like a good survey of what is known about the effect of extreme exertion on the heart. It shows evidence that the hearts of highly trained athletes can enlarge and thicken in a way that would be seen as worrying for a normal person and there can also be scarring and other damage. However we don’t know enough about what that means for overall health and longevity, as the authors recognise in the abstract: 

However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity.

Nevertheless there is enough in this paper to get one thinking. But it must be emphasised that the authors are not warning about exercise of itself, instead they are raising the question as to whether there can be too much of a good thing. They explicitly offer no excuse for the couch potato to remain inert as their opening sentences make clear:

Regular exercise is one of the cornerstones of therapeutic lifestyle changes for producing optimal cardiovascular (CV) and overall health. Physical exercise, though not a drug, possesses many traits of a powerful pharmacological agent. A routine of daily physical activity (PA) stimulates a number of beneficial physiologic changes in the body and can be highly effective for prevention and treatment of many of our most prevalent and pernicious chronic diseases, including coronary heart disease (CHD), hypertension, heart failure, obesity, depression, and diabetes mellitus.1 People who exercise regularly have markedly lower rates of disability and a mean life expectancy that is 7 years longer than that of their physically inactive contemporaries.

The point needs to be emphasised because there is no way you want a simplified message that running is bad for your health to seep into the public consciousness. It shouldn’t from this paper, which is a restrained academic review that does not editorialise. However that is done by the authors in the BMJ journal Heart, where they are clearer in describing the effect of exercise as a U curve where too much high intensity work loses some of the gains of a more moderate regime. (It can be found here but unless you have a subscription or access from a library it is not worth the £24 they want to charge. Instead watch the TED talk that covers the same ground). 

The article has caused more controversy because it inspired the article in the Wall Street Journal I previously mentioned. As is common for newspapers the headline and opening paragraphs were overly alarming, even if there was more balance further down the piece (as is also common in newspapers). This has been a push back with some people to contest the conclusions (e.g. here and here) and a little flurry of concern.

My take (for what it’s worth - and that is very little because it is just the intuitive response of someone who runs about a bit) is that I am very ready to believe that there is a sweet spot for exercise to offer maximum health benefits, which might not accord with the amount of work needed to fulfil other ambitions. It is very likely that more might not mean better especially for those of us over 50. But I am not sure if I have to worry too much. I may be old but the amount of running I do faster than 8 min miles is vanishingly small. I, like most people, am probably well within the boundaries of exercise being a good thing. However the problem is we cannot precisely define where those boundaries are. Take for example easy exercise: apparently we can walk as much as we like without hitting  a point of diminishing returns but does that also apply to slow, low intensity running?  If so the majority people who run marathons have no worries because, from the middle to the back of the pack, the long slow running dominates training (and the race). For most people the debate about a U shaped exercise curve is irrelevant because we don’t run hard or fast enough to reach the bottom of the U. The people at risk are the seriously competitive and they are the very people whose motivation has nothing to do with wellbeing or health. But the amount of that risk, if at all, is not yet known. 

It is all neatly summed up in an article in Outside about the original Mayo review: “high-intensity, high-volume exercise is really, at this point, a black box in terms it what it does for you over the long haul.”


Calgary Podiatrist said...

This is disturbing. I think I better go lie down some more.

JoggingLife said...

I think you're spot on when you say "The people at risk are the seriously competitive and they are the very people whose motivation has nothing to do with wellbeing or health."

For the vast majority of people, running will be highly beneficial.

For the elite few who may be pushing things too far... well - this is obviously all unconfirmed - but even if it were proven to be true, elites would push themselves just as hard anyway. Because it's what they do, and what they love.